It is known that circuit breakers in power distribution networks can be operated on connection and disconnection such that the load on the respective circuit breaker is as low as possible, especially also with regard to contact erosion and to the generation of overvoltages or overcurrents as a result of the respective switching operation.
Laid-open Specification DE 1 565 995 discloses a device which allows mains-synchronous tripping of an AC circuit breaker. A current measurement and a voltage measurement are provided in this device, and generate the two measurement signals which are fed to the actual control device for synchronization. This measurement is normally carried out on the mains side of the circuit breaker, since the mains voltage is always present on this side and is used as a reference value for mains-synchronous switching. No voltage measurement is provided on the load side of the circuit breaker, since, when the load is disconnected, there is no voltage on this side which could be used as a reference value for mains-synchronous switching.
However, switchgear assembly configurations exist in which the load flow direction is not clearly defined by the circuit breaker. In switchgear assemblies such as these, mains-synchronous switching is not possible in all operating situations by means of the described device.